Multipath cross flow heat exchanger

ABSTRACT

The present invention relates to a multipath cross flow heat exchanger and, more particularly, to a multipath cross flow heat exchanger, capable of preventing degradation of the cooling performance for cooling a superconductor which may occur when circulation of liquid nitrogen in a circulation tube is not efficient, by forming a cooling tube, in which a refrigerant for cooling liquid nitrogen flows, to intersect multiple times with the circulation tube, in which the liquid nitrogen is circulated, to thereby freeze the liquid nitrogen by the refrigerant.

TECHNICAL FIELD

The present invention relates to a multipath cross flow heat exchangerand, more particularly, to a multipath cross flow heat exchanger,capable of preventing degradation of the cooling performance for coolinga superconductor which may occur when circulation of liquid nitrogen ina circulation tube is not efficient, by forming a cooling tube, in whicha refrigerant for cooling liquid nitrogen flows, to intersect multipletimes with the circulation tube, in which the liquid nitrogen iscirculated, to thereby freeze the liquid nitrogen by the refrigerant.

The present application claims the benefit of Korean Patent ApplicationNo. 10-2013-0082388, filed on Jul. 12, 2013, the contents of which areentirely incorporated herein by reference.

BACKGROUND ART

As well known to those skilled in the art, a superconductor is aconductor showing superconductivity, a phenomenon wherein near-zeroelectrical resistance can be reached at a very low temperature. Magneticfields cannot penetrate into the superconductor, and magnetic fieldsalready present therein are expulsed, thereby producing a magneticlevitation effect when placed over a magnet.

The superconductor having such a property may be used in various fieldssuch as a fault current limiter controlling electric power, magneticlevitation technology, and power transmission.

Particularly, in the field of power transmission, as the length of asuperconducting cable increases, heat transfer thereto from outsideincreases, and when alternating current flows in the superconductingcable, the temperature thereof increases, thereby generating power lossand increasing cooling load.

That is, to maintain the near-zero electrical resistance of thesuperconductor, it is important to maintain the superconductor at anultra-low temperature by cooling the superconductor.

As described above, to maintain a superconducting device at ultra-lowtemperature, liquid nitrogen at an ultra-low temperature for cooling thesuperconducting cable is used, and heat exchange between the liquidnitrogen and the superconducting cable increases the temperature of theliquid nitrogen, and thus it is required to have an additional coolingsystem for cooling the liquid nitrogen.

An example of prior art documents related to the present invention maybe referred to Korean Patent No. 10-0124825 (Published on Dec. 3, 2009,entitled Cooling system for a superconducting fault current limiterusing solid cryogens).

DISCLOSURE Technical Problem

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a multipath cross flow heat exchangerconstructed in such a manner that a cooling tube, in which a refrigerantfor cooling a cooling fluid flows, intersects multiple times thecirculation tube in which the cooling fluid for cooling asuperconducting cable flows, thereby preventing the cooling fluid fromfreezing and the cooling performance of the cooling fluid fromdegrading.

An object of the present invention having the above-mentionedconstruction is to provide a heat exchanger that does not require theinstallation of a heater for preventing the cooling fluid from freezing.

Technical Solution

In order to accomplish the above object, the present invention providesa multi-path cross flow heat exchanger including: a circulation tube inwhich cooling fluid for cooling a superconducting cable flows; and acooling tube defining a flowing path intersecting the circulation tubemultiple times and in which a refrigerant that exchanges heat with thecooling fluid flows.

The circulation tube and the cooling tube may intersect each other whilebeing isolated from each other so that the cooling fluid in thecirculation tube and the refrigerant in the cooling tube are preventedfrom being mixed together.

The cooling tube may be constructed in such a manner that when thecooling fluid flows from a first end to a second end of the circulationtube, a position at which the refrigerant flowing in the cooling tubeprimarily intersects the circulation tube is located at the second endof the circulation tube, and another position at which the refrigerantcompleting heat exchange with the cooling fluid in the cooling tubesecondarily intersects the circulation tube is located at the first endof the circulation tube.

The cooling tube may be constructed to have a diameter larger than adiameter of the circulation tube, and the circulation tube is located inthe cooling tube at positions at which the circulation tube and thecooling tube intersect each other, so that heat exchange between thecooling fluid and the refrigerant occurs on an outer surface of thecirculation tube at portions at which the circulation tube intersectsthe cooling tube.

The cooling tube may include: a body part having a housing-shapedstructure and defining a space part therein, the space part including apredetermined part of the circulation tube; a supply part provided on aposition of an outer surface of the body part and supplying therefrigerant to the space part; and a discharge part provided on anotherposition of an outer surface of the body part and through which therefrigerant supplied to the space part is discharged.

The circulation tube may be divided into multiple branch tubes in anarea at which the circulation tube intersects the cooling tube, whereineach of the multiple branch tubes has a diameter smaller than thediameter of the circulation tube.

The supply part and the discharge part may be located at one side basedon the circulation tube passing through the body part, and be spacedapart from each other on an outer surface of the cooling tube.

The body part may further include: a partition wall arranged in thespace part defined in the body part at a location between the supplypart and the discharge part, wherein the partition wall is provided withan opening part through which the refrigerant passes such that therefrigerant supplied to the space part through the supply part can bedischarged through the discharge part.

Advantageous Effects

As described above, the present invention has an advantage preventingthe cooling fluid from being frozen and the cooling performance of thecooling fluid from degrading.

Accordingly, the present invention has another advantage in that it doesnot require installing a heater for preventing the cooling fluid fromfreezing

DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing the first embodiment of the multipath crossflow heat exchanger according to the present invention;

FIG. 2 is a schematic diagram showing heat exchange of the secondembodiment of the multipath cross flow heat exchanger according to thepresent invention;

FIG. 3 is a view showing various embodiments of the multipath cross flowheat exchanger according to the present invention;

FIG. 4 is a view showing the outline of a cooling fluid behavior and thedistribution of the cooling fluid temperature of the multipath crossflow heat exchanger according to the present invention;

FIG. 5 is a view showing the outline of a cooling fluid behavior and thedistribution of the cooling fluid temperature of a parallel-flow heatexchanger; and

FIG. 6 is a view showing the outline of a cooling fluid behavior and thedistribution of the cooling fluid temperature of a cross flow heatexchanger.

MODE FOR INVENTION

The present invention will be described in detail below with referenceto the accompanying drawings.

Here, repeated descriptions and descriptions of known functions andconfigurations that have been deemed to make the gist of the presentinvention unnecessarily obscure will be omitted below.

And the embodiments of the present invention are intended to fullydescribe the present invention to a person having ordinary knowledge inthe art to which the present invention pertains.

Accordingly, the shapes, sizes, etc. of components in the drawings maybe exaggerated to make the description clearer.

FIG. 1 is a view showing the first embodiment of the multipath crossflow heat exchanger according to the present invention.

Referring to FIG. 1, the multipath cross flow heat exchanger accordingto the present invention includes: a circulation tube 100 in whichcooling fluid for cooling a superconducting cable flows; and a coolingtube 200 defining a flowing path intersecting the circulation tube 100multiple times and in which a refrigerant that exchanges heat with thecooling fluid flows.

Here, the following describes a heat exchange process through which thecooling fluid is deprived of heat by the refrigerant while thecirculation tube 100 and the cooling tube 200 intersect each other. Thecirculation tube and the cooling tube intersect each other while beingisolated from each other so that the cooling fluid in the circulationtube 100 and the refrigerant in the cooling tube 200 are prevented frombeing mixed together.

That is, the cooling fluid and the refrigerant are prevented from beingmixed together and heat exchange occurs at the circulation tube 100 inwhich the cooling fluid flows.

The circulation tube 100 and the cooling tube 200 can exchange heat witheach other in the following configuration.

The cooling tube 200 includes: a body part 210 having a housing-shapedstructure and defining a space part S therein, the space part Sincluding a predetermined part of the circulation tube 100; a supplypart 220 provided on a position of an outer surface of the body part 210and supplying the refrigerant to the space part S; and a discharge part230 provided on another position of an outer surface of the body part210 and through which the refrigerant supplied to the space part S isdischarged.

As illustrated in FIG. 1, the supply part 220 and the discharge part 230are located at one side (the same side) based on the circulation tube100 passing through the body part 210, and are spaced apart from eachother on an outer surface of the cooling tube.

The following details describe the heat exchange process of the heatexchanger of the present invention described in FIG. 1 as a firstembodiment. The cooling fluid flows from the left side to the right sideof the circulation tube 100, and the refrigerant is supplied to the bodypart through the supply part 220, and the refrigerant is in thermalcontact with the outer surface of the circulation tube 100 in the bodypart 210, thereby exchanging heat with the cooling fluid flowing in thecirculation tube and being discharged through the discharge part 230.

By using the heat exchanger having the above-mentioned constructionaccording to the present invention, the heat exchanger can prevent thecooling fluid from freezing and can maintain efficient coolingperformance of the cooling fluid. The heat exchange process is describedfurther in detail below.

FIG. 2 is a schematic diagram showing heat exchange of the secondembodiment of the multipath cross flow heat exchanger according to thepresent invention.

Referring to FIG. 2, the cooling tube 200 is constructed in such amanner that when the cooling fluid flows from a first end to a secondend of the circulation tube 100, a position P1 at which the refrigerantflowing in the cooling tube 200 primarily intersects the circulationtube 100 is located at the second end of the circulation tube 100, andanother position P2, at which the refrigerant completing heat exchangewith the cooling fluid in the cooling tube 200, secondly intersects thecirculation tube 100, is located at the first end of the circulationtube 100.

As shown in FIG. 2, the circulation tube 100 is divided into multiplebranch tubes 110 in an area at which the circulation tube 100 intersectsthe cooling tube 200, wherein each of the multiple branch tubes has adiameter smaller than the diameter of the circulation tube 100.

As described above, the multiple branch tubes 110 are selectivelyconnected to the circulation tube 100 according to the requirements offacilities using the superconducting cable, thereby increasing theefficiency of the cooling performance of the heat exchanger.

In addition, the body part 210 further comprises: a partition wall 240arranged in the space part S defined in the body part at a locationbetween the supply part 220 and the discharge part 230, wherein thepartition wall 240 is provided with an opening part 241 through whichthe refrigerant passes such that the refrigerant supplied to the spacepart S through the supply part can be discharged through the dischargepart 230.

That is, referring to FIG. 2, the refrigerant flows in an “∩” shape inthe space part S, thereby cooling the cooling fluid.

Referring to FIG. 2, the following details describe the heat exchangeprocess of the second embodiment of the multipath cross flow heatexchanger. The cooling fluid for cooling the superconducting cable flowsfrom the left side to the right side of the circulation tube 100 to passthrough the body part 210 of the cooling tube 200.

As illustrated in FIG. 2, the circulation tube may be divided intomultiple branch tubes 110 in the body part 210 when it is desired.

The refrigerant for cooling the cooling fluid flows into the body part210, or the space part S through the supply part 220.

The refrigerant first exchanges heat with the cooling fluid on the outersurface of the circulation tube 100 at the position P1 in the space partS, thereby first cooling the cooling fluid.

The refrigerant passing through the position P1 changes its flowingdirection to the left side of the circulation tube 100 while hitting theinner wall of the body part 210, and the refrigerant changing itsflowing direction passes through the position P2 in the space part S,thereby secondarily exchanging heat with the cooling fluid and beingdischarged from the body part 210 through the discharge part 230.

The multipath cross flow heat exchanger according to the presentinvention may be designed in the following various embodiments accordingto cooling performance required in facilities for cooling thesuperconducting cable.

FIG. 3 is a view showing various embodiments of the multipath cross flowheat exchanger according to the present invention.

As described above, FIG. 3a is a view showing an embodiment of astructure constructed in such a manner that a cooling fluid and arefrigerant first exchange heat at the position P1 and second exchangeheat at the position P2.

A detailed description of the above-mentioned heat exchange process isomitted since it is the same as described above.

FIG. 3b is a view showing another embodiment of the structureconstructed in such a manner that the refrigerant passing through theposition P2 is not discharged through a discharge part 230 but therefrigerant changes its flowing direction again, thereby exchanging heatwith the cooling fluid three times prior to being discharged through thedischarge part 230.

As illustrated in FIG. 3b , FIG. 3c is a view showing still anotherembodiment of the structure constructed in such a manner that therefrigerant supplied to a space part S through a supply part 220intersects a circulation tube 100 four times in the space part, therebyexchanging heat with the cooling fluid four times.

FIG. 4 is a view outlining the cooling fluid behavior and thedistribution of the cooling fluid temperature of the multipath crossflow heat exchanger according to the present invention, FIG. 5 is a viewoutlining the cooling fluid behavior and the distribution of the coolingfluid temperature of a parallel-flow heat exchanger, and FIG. 6 is aview outlining the cooling fluid behavior and the distribution of thecooling fluid temperature of a cross flow heat exchanger.

First, FIG. 4 is a view showing the cooling fluid behavior and thedistribution of the cooling fluid temperature of the multipath crossflow heat exchanger according to the present invention, and shows thatin a normal load state, liquid nitrogen can efficiently flow withoutfreezing in the circulation tube 100.

Here, temperature distribution lines (unit: absolute temperature, K) areconcentrated around the supply part 220 through which the refrigerantbegins to be supplied, and the lowest temperature is 64K, and thus theliquid nitrogen can efficiently flow without freezing

In a low-load state, the lowest temperature around the supply part 220is 63K, and an area indicating 63K is such a small frozen area that theliquid nitrogen is not prevented from flowing in the circulation tube100.

A parallel-flow method shown in FIG. 5, which is generally used, refersto the method operated in such a manner that liquid nitrogen in acirculation tube 100 flows in a direction contrary to a refrigerant in acooling tube 200. The parallel-flow method is excellent in coolingefficiency, and thus it is widely used.

As shown in FIG. 5, in the parallel-flow method, the liquid nitrogenefficiently flows without freezing in a normal load state. However, in alow-load state, the lowest temperature approaches 62K, and the liquidnitrogen is frozen in a 62K area or an area lower than 62K, includingtemperature distribution lines around 63K.

Accordingly, compared to the frozen area of the low-load state of FIG.4, the liquid nitrogen in the low-load state of the parallel-flow methodis frozen in areas ranging from 62K to 63K in the circulation tube 100,so that the liquid nitrogen is prevented from flowing in the circulationtube 100.

FIG. 6 shows the cross flow heat exchanger constructed in such a mannerthat a refrigerant in a cooling tube 200 flows in a directionperpendicular to liquid nitrogen in a circulation tube 100.

In the cross flow heat exchanger, as shown in FIG. 6, even in a normalload state, a frozen area is formed in which some of the liquid nitrogenis frozen in the circulation tube 100. Even in a normal load state, thefrozen area of the liquid nitrogen in the cross flow heat exchanger islarger than the frozen area of the liquid nitrogen in the multipathcross flow heat exchanger in the low-load state according to the presentinvention shown in FIG. 4.

As described above, in the cross flow heat exchanger, a flowing area asmuch as or more than ⅓ thereof is frozen even in the normal load state,thereby the liquid nitrogen being prevented from flowing in thecirculation tube 100, and if the cross flow heat exchanger in the statecontinues to be operated, it is required to install and operate at alltimes an additional heater for safety.

In the cross flow heat exchanger, it is shown that the amount of frozenliquid nitrogen in the low-load state is more than the amount of liquidnitrogen in the normal load state.

As described above, by using the multipath cross flow heat exchangeraccording to the present invention, the liquid nitrogen in the normalload state is prevented from freezing in the circulation tube 100. Andeven the liquid nitrogen in the low-load state is frozen in a very smallarea, so that the liquid nitrogen is not prevented from flowing in thecirculation tube 100, thereby realizing the efficient flow of the liquidnitrogen and preventing the cooling performance for cooling thesuperconducting cable from degrading.

Additionally, the frozen area of the liquid nitrogen is so small that itis not required to install an additional heater to heat the circulationtube 100 to solve the problems, thereby increasing the efficiency of acooling system, and removing or decreasing energy consumption caused byoperating the heater.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, the spirit of the present inventionis not limited to the accompanying drawings and the above-mentioneddescription, and those skilled in the art will appreciate that variousmodifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. A multipath cross flow heat exchanger comprising:a circulation tube in which cooling fluid for cooling a superconductingcable flows; and a cooling tube defining a flowing path intersecting thecirculation tube multiple times and in which a refrigerant thatexchanges heat with the cooling fluid flows.
 2. The multipath cross flowheat exchanger of claim 1, wherein the circulation tube and the coolingtube intersect each other while being isolated from each other so thatthe cooling fluid in the circulation tube and the refrigerant in thecooling tube are prevented from being mixed together.
 3. The multipathcross flow heat exchanger of claim 1, wherein the cooling tube isconstructed in such a manner that when the cooling fluid flows from afirst end to a second end of the circulation tube, a position at whichthe refrigerant flowing in the cooling tube primarily intersects thecirculation tube is located at the second end of the circulation tube,and another position at which the refrigerant completing heat exchangewith the cooling fluid in the cooling tube secondarily intersects thecirculation tube is located at the first end of the circulation tube. 4.The multipath cross flow heat exchanger of claim 1, wherein the coolingtube is constructed to have a diameter larger than a diameter of thecirculation tube, and the circulation tube is located in the coolingtube at positions at which the circulation tube and the cooling tubeintersect each other, so that heat exchange between the cooling fluidand the refrigerant occurs at an outer surface of the circulation tubeat portions at which the circulation tube intersects the cooling tube.5. The multipath cross flow heat exchanger of claim 1, wherein thecooling tube comprises: a body part having a housing-shaped structureand defining a space part therein, the space part including apredetermined part of the circulation tube; a supply part provided on aposition of an outer surface of the body part and supplying therefrigerant to the space part; and a discharge part provided on anotherposition of an outer surface of the body part and through which therefrigerant supplied to the space part is discharged.
 6. The multipathcross flow heat exchanger of claim 5, wherein the circulation tube isdivided into multiple branch tubes in an area at which the circulationtube intersects the cooling tube, wherein each of the multiple branchtubes has a diameter smaller than the diameter of the circulation tube.7. The multipath cross flow heat exchanger of claim 5, wherein thesupply part and the discharge part are located at one side based on thecirculation tube passing through the body part, and are spaced apartfrom each other on an outer surface of the cooling tube.
 8. Themultipath cross flow heat exchanger of claim 6, wherein the body partfurther comprises: a partition wall arranged in the space part definedin the body part at a location between the supply part and the dischargepart, wherein the partition wall is provided with an opening partthrough which the refrigerant passes such that the refrigerant suppliedto the space part through the supply part can be discharged through thedischarge part.